Using algae or cyanobacteria to produce carbon compounds photosynthetically from CO2 and water has theoretical potential but has yet to be realized on an industrial scale. One major limitation is that these cells are naturally high in protein, especially under conditions that lead to maximum growth rates. Thus a large fraction of carbon from photosynthesis is used to produce nitrogen containing amino acids rather than other products containing only carbon, hydrogen, and oxygen. When nitrogen sources are removed from cultures of non-diazotrophic cyanobacteria, cells accumulate high concentrations of glycogen, but large-scale harvesting of microbial oxygenic phototrophs is difficult and expensive with currently available technologies.
Alpha ketoglutarate (AKG) is used as an organic synthesis intermediate, a medicine ingredient, a biochemical reagent, and as a nutritional additive in food and sport drinks Currently AKG is produced by chemical synthesis using triethyl oxalosuccinic ester derived from petroleum and concentrated hydrochloric acid, or by fermentation using sugar as feedstock. Photosynthetic production of AKG could therefore replace petroleum or sugar as the feedstock and eliminate the use of corrosive acid.
Ethylene is used in the synthesis of diverse products from plastics (e.g., polyethylene, polystyrene, and PVC) to textiles such as polyester. Ethylene has been used to produce high-grade ethanol industrially for the past 50 years, by a relatively simple catalytic process involving the hydration of ethylene into ethanol. In addition, the technology to polymerize ethylene to gasoline has been known for nearly a century. Ethylene is the most widely produced organic compound globally, with more than 132.9 million tons produced in 2010 and projected growth of 5% a year through 2015.
The current method of producing ethylene is via steam cracking of long chain hydrocarbons from petroleum, or via dehydrogenation of ethane. Unfortunately, fossil fuel supplies are finite and utilization of these feed stocks produces greenhouse gases such as CO2 (1.5 to 3.0 tons CO2 per ton of ethylene). For these reasons, sustainable, carbon neutral processes that are capable of producing this essential chemical are needed. One such alternative is the use of biological processes to convert CO2 or other waste products into ethylene. Based on the overall equation 2CO2+2H2O═C2H4+3O2, photosynthetic production of one ton of ethylene could sequester 3.14 tons of CO2.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.